Lubricant composition

ABSTRACT

Disclosed is a lubricant composition containing a compound of formula (1) and a carboxylic acid, and exhibiting excellent lubrication potency.  
                 
 
wherein D represents a cyclic group; X represents a single bond, a group NR 1  (where R 1  represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group; m indicates an integer of from 2 to 11.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention belongs to a technical field of a lubricant composition that is fed to mechanical friction slide members, more precisely to a technical field of a lubricant composition that has good low-friction characteristics and good abrasion resistance under extreme pressure and is excellent in the durability of the effects.

2. Description of the Background

The properties that lubricant is desired to have are that it can lower the friction factor of mechanical friction slide members in a broad temperature range and in a broad pressure range and it can maintain the effect as long as possible. Not only the effect of improving the lubricity between friction slide members, lubricant is further desired to have an effect of imparting abrasion resistance to friction slide members themselves. The effect of lubricant such as engine oil of reducing the friction factor of friction slide members and the prolongation of the life of lubricant are directly connected with the improvement in fuel efficiency, or that is, energy saving in machine driving. The prolongation of the life of engine oil enables not only the reduction in the amount of waste oil but also the reduction in the amount of CO₂ exhaust, and is therefore favorable in point of the ecological requirements that have become specifically noted these days. Of slide members of industrial machines, bearings and gears are slid under especially severe friction conditions, and if conventional lubricants such lube oil or grease are applied to such slide members, then they may cause lubrication failure or seizure when the lubrication conditions are severer, and therefore they could not attain the desired low friction factor owing to scratches formed by abrasion. As a result, it may lose the reliability of devices. In particular, when devices are down-sized, the friction conditions at the slide members are apt to be severer, and it is a bar to down-sizing of devices. Accordingly, energy-saving lubricants are desired which can improve the reliability of devices, not causing abrasion and seizure even under severe conditions, and can contribute toward down-sizing of devices.

Conventional lubricant heretofore known in the art generally comprises, as the principal component thereof, a lubricant base oil and contains a lubricant aid such as an organic compound added thereto. Recently, in particular, an organic molybdenum compound has become specifically noted as a lubricant aid. The organic molybdenum compound can exhibit good properties including good abrasion resistance, good extreme-pressure resistance (load resistance) and low-friction characteristics, even when slide members of machine devices are driven at high temperatures, at high speed or low speed and under high load and even when they are down-sized and lightweight, and can effectively exhibit good lubrication potency under high pressure conditions, or that is, under boundary lubrication conditions rather than under ordinary pressure. Accordingly, the compound is specifically noted as a material capable of exhibiting such specific lubrication potency.

The organic molybdenum compound is an excellent material capable of exhibiting excellent lubrication effects even under severe friction conditions. On the other hand, however, lubricant that contains such an organic molybdenum compound may contain heavy metals such as molybdenum and zinc, as well as sulfides that are readily oxidized into sulfur oxides to have some negative influences not only on the lubricant but also on slide members themselves and even on the environment, and phosphoric acid compounds that may eutrophicate rivers and seas, and the amount of such contaminants is large and is obviously unfavorable from the viewpoint of ecological requirements. Further, the molybdenum oxide/sulfide film formed on the slide face is gradually cut off owing to friction, and a new film is formed. Accordingly, when any of the organic molybdenum compound or the organic zinc compound that is a source to form the film becomes insufficient, the lubricant may rapidly lose its effect. However, if the amount of the organic molybdenum compound and the organic zinc compound in the lubricant is increased, then the side products from the peeled film may increase in the system, and they may have some negative influences on the slide machines themselves. Therefore, increasing the compounds is not effective. In fact, in the system where the organic molybdenum compound is used, the effect of improving fuel efficiency could not be expected so much from the prolongation of the life of the lubricant used. To that effect, conventional lubricants are all unsatisfactory, and no one has heretofore succeeded in providing good lubricant capable of exhibiting good lubrication potency and capable of maintaining the effect for a long period of time, not containing environmental harmful substances or environmental contaminant substances such as heavy metal elements, phosphoric acid compounds and sulfides.

We, the present inventors have assiduously studied for solving the problems with lubricant in the related art, and have previously found that a lubricant composition comprising, as the principal component thereof, a triazine structure-having compound well satisfies the ecological requirements and has a prolonged life to improve the fuel efficiency in machines, therefore exhibiting good lubrication potency useful as a friction factor-reducing agent, an extreme-pressure agent and an abrasion inhibitor (JP-A 2003-64390). However, lubricant is required to have various properties and is now required to have higher-level lubrication potency since various machines are now improved to have better performance so as to be able to be driven under severer conditions.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the various problems mentioned above, and its object is to provide a lubricant composition capable of exhibiting excellent lubrication potency not only in the form of a mixture with a conventional lubricant base oil but also in any other form not mixed with such a lubricant base oil. Another object of the invention is to provide a lubricant composition capable of maintaining low friction and good abrasion resistance on slide faces for a long period of time, especially capable of maintaining low friction and good abrasion resistance thereon even under extreme pressure. Still another object of the invention is to provide a lubricant composition which does not contain any of heavy metal elements, phosphate groups and sulfides all inconsistent with ecological requirements, and which therefore prolongs the life thereof and satisfies ecological requirements.

We, the present inventors have assiduously studied for solving the problems with lubricant in the related art, and now have found that a compound having a specific functional group moiety structure exhibits excellent lubrication potency, and, on the basis of this finding, we have completed the present invention.

Specifically, the objects of the invention are attained by a lubricant composition of any of the following (1) to (13):

(1) A lubricant composition containing a compound of the following formula (1) and a compound of the following formula (2):

wherein D represents a cyclic group capable of bonding to m groups of side branches; X independently represents a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group consisting of a combination thereof; R independently represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group; m indicates an integer of from 2 to 11,

wherein R³¹ represents an alkyl group, analkenyl group, an alkynyl group, or a cycloalkyl group.

(2) The lubricant composition of (1), wherein Din formula (1) is a 5- to 7-membered heterocyclic group.

(3) The lubricant composition of (1) or (2), wherein at least one of m groups of Rs in formula (1) contains an ester bond.

(4) The lubricant composition of any one of (1) to (3), wherein the compound of formula (1) is represented by the following formula (3):

wherein X¹, X² and X³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R¹¹, R¹² and R¹³ each independently represent an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, and at least one of R¹¹, R¹² and R¹³ contains an ester bond.

(5) The lubricant composition of (4), wherein X¹, X² and X³ in formula (3) are —NH—.

(6) The lubricant composition of any one of (1) to (5), wherein the compound of formula (1) is represented by the following formula (4):

wherein X²¹, X²² and X²³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R²¹, R²² and R²³ each independently represent a substituent, and at least one of R²¹, R²² and R²³ contains an ester bond; a21, a22 and a23 each independently indicate an integer of from 1 to 5.

(7) The lubricant composition of (6), wherein at least one of R²¹, R²² and R²³ in formula (4) is an alkoxy group substituted with a substituent having an ester bond-containing, linear or branched alkyl group.

(8) The lubricant composition of (6) or (7), wherein X²¹, X²² and X²³ in formula (4) are —NH—.

(9) The lubricant composition of any one of (1) to (8), wherein R³¹ in formula (2) is an alkyl, alkenyl, alkynyl or cycloalkyl group substituted with a substituent that contains an alkyl chain having at least 4 carbon atoms in total, an alkyleneoxy chain, a polyfluoroalkyl chain having at least 2 carbon atoms in total, or an organic polysilyl chain.

(10) The lubricant composition of any one of (1) to (8), wherein R³¹ in formula (2) is an alkyl group substituted with an alkyleneoxy chain-containing substituent.

(11) The lubricant composition of any one of (1) to (10), wherein the compound of formula (1) and the compound of formula (2) form complexes.

(12) The lubricant composition of any one of (1) to (11), which contains from 0.5 to 5 mols of the compound of formula (2) relative to one mol of the compound of formula (1).

(13) The lubricant composition of any one of (1) to (11), which contains from 2 to 4 mols of the compound of formula (2) relative to one mol of the compound of formula (1).

According to the invention, there is provided a practicable lubricant composition that exhibits good abrasion resistance, extreme pressure resistance and low friction characteristics when applied to mechanical friction slide members. In addition, the lubricant composition of the invention exhibits excellent lubrication potency even in a broad temperature range.

BEST MODE FOR CARRYING OUT THE INVENTION

The lubricant composition of the invention is described in detail hereinunder. The lubricant composition of the invention is characterized by containing a specific cyclic-structured compound and a specific carboxylic acid as the principal components thereof.

[Cyclic-Structured Compound]

The cyclic-structured compound to be in the lubricant composition of the invention is a discotic compound of formula (1). The discotic compound is characterized in that it has a discotic molecular moiety at the center thereof. The morphological characteristic of the discotic center, except the side branches around it, of the compound may be expressed as follows, for example, for the hydrogen-substituted skeleton compound. The molecular size may be obtained as follows:

1) The molecule as flat as possible, preferably having a flat molecular structure is constructed. In this case, the bond distance and the bond angle are preferably standard values corresponding to the mixture of orbits. For example, Chemical Handbook, revised 4th edition of Basic Chemistry, second separate volume, chapter 15 (by the Chemical Society of Japan, Maruzen, 1993) may be referred to.

2) Based on the initial value of the structure obtained in the above 1), the molecular structure is optimized according to a molecular orbital method or a molecular force field method. For the method, for example, employable are Gaussian 92, MOPAC 93, CHARMm/QUANTA, MM3. Preferred is Gaussian 92.

3) The center of gravity of the structure that has been obtained in the mode of structure optimization as above is moved to the origin thereof, and the coordinate axis is taken on the principal axis of inertia (the principal axis of the inertial tensor ellipsoid).

4) A sphere defined by the van der Waals radius thereof is imparted to every atom, by which the morphology of the molecule is described.

5) The length in each coordinate axis direction is measured on the van der Waals surface, and it is referred to as a, b, c.

With the values a, b and c obtained according to the process as above, when the disc morphology of the structure is defined, then a≧b>c and a≧b≧a/2, preferably a≧b>c and a≧b≧0.7a. Also preferably, b/2>c.

For the specific examples of the discotic compounds, there are mentioned nuclear compound derivatives, for example, as in Quarterly General Chemistry, No. 22Chemistry of Liquid Crystal, Chap. 5, Chap. 10, Sec. 2 (by the Chemical Society of Japan, the Society Publishing Center, 1994); C. Destrade et al's Study Report, Mol. Cryst. Liq. Cryst., Vol. 71, p. 111 (1981); B. Kohne et al's Study Report, Angew. Chem., Vol. 96, p. 70 (1984); J. M. Lehn et al's Study Report, J. Chem. Soc. Chem. Commun., p. 1794 (1985); J. Zhang, J. S. Moore et al's Study Report, J. Am. Chem. Soc., Vol. 116, p. 2655 (1944).

For example, they include benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives, porphyrin derivatives, anthracene derivatives, hexaethynylbenzene derivatives, dibenzopyrene derivatives, coronene derivatives and phenylacetylene-macrocycle derivatives. Further mentioned herein are cyclic compounds and their hetero atom-substituted electronic structures as in General Chemistry, No. 15 New Aromatic Chemistry (by the Chemical Society of Japan, the Tokyo University Publishing, 1977).

The compound of formula (1) to be in the lubricant composition of the invention is described in detail.

In formula (1), D represents a cyclic group capable of bonding tom groups of side branches; X independently represents a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R independently represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group; m indicates an integer of from 2 to 11.

In formula (1), D is preferably an aromatic group or a heterocyclic group. The aromatic ring of the aromatic group includes, for example, benzene ring, indene ring, naphthalene ring, triphenylene ring, fluorene ring, phenanthrene ring, anthracene ring, and pyrene ring. The aromatic group may be substituted. The heterocyclic group preferably has a 5-, 6- or 7-membered hetero ring, more preferably a 5-membered or 6-membered hetero ring, most preferably a 6-membered hetero ring. The hetero atoms to constitute the hetero ring are preferably, nitrogen, oxygen and sulfur atoms. The hetero ring is preferably an aromatic hetero ring. The aromatic hetero ring is generally an unsaturated hetero ring. More preferably, the hetero ring is an unsaturated hetero ring having a largest number of double bonds. The hetero ring includes, for example, furan ring, thiophene ring, pyrrole ring, pyrroline ring, pyrrolidine ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, imidazoline ring, imidazolidine ring, pyrazole ring, pyrazoline ring, pyrazolidine ring, triazole ring, furazane ring, tetrazole ring, pyran ring, thiyne ring, pyridine ring, piperidine ring, oxazine ring, morpholine ring, thiazine ring, pyridazine ring, pyrimidine ring, pyrazine ring, piperazine ring, and triazine ring. Preferred is a triazine ring, and for example, it is a 1,3,5-triazine ring. The hetero ring may be condensed with any other hetero ring, aliphatic ring or aromatic ring. However, monocyclic hetero rings are preferred herein.

In formula (1), X is a single bond, a group NR¹ (where R¹ is a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof. When X is a single bond, then the substituent may directly bond to the heterocyclic group via the nitrogen atom having a free atomic valence, like in piperidine, or even when the heterocyclic group does not have a free atomic valence, the substituent may bond to the hetero atom to form onium salts such as oxonium salts, sulfonium salts or ammonium salts. X in formula (1) is preferably a sulfur atom or a group NR¹, in which R¹ is preferably an alkyl group having at most 3 carbon atoms, or a hydrogen atom.

In formula (1), when R is an alkyl group, it preferably has from 1 to 30 carbon atoms, more preferably from 2 to 30, even more preferably from 4 to 30, still more preferably from 6 to 30 carbon atoms. The alkyl group may be linear or branched.

It may be substituted. Examples of the substituent include a halogen atom, an alkoxy group (e.g., methoxy, ethoxy, methoxyethoxy, phenoxy), a sulfido group (e.g., methylthio, ethylthio, propylthio), an alkylamino group (e.g., methylamino, propylamino), an acyl group (e.g., acetyl, propanoyl, octanoyl, benzoyl), an acyloxy group (e.g., acetoxy, pivaloyloxy, benzoyloxy), a hydroxyl group, a mercapto group, an amino group, a carboxyl group, a sulfo group, a carbamoyl group, a sulfamoyl group, and an ureido group.

In formula (1), when R is an alkenyl group or an alkynyl group, the number of carbon atoms constituting the group and the morphology of the group may be the same as those of the alkyl group, and the group may be substituted like the alkyl group.

In formula (1), when R is an aryl group, it includes a phenyl group, an indenyl group, an a-naphthyl group, a β-naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, and pyrenyl group. Preferred are a phenyl group and a naphthyl group. The aryl group may be substituted. Examples of the substituent are those mentioned hereinabove for the alkyl group, and an alkyl group. Preferably, the group is substituted with a substituent that contains a linear or branched alkyl group having at least 8 carbon atoms, for example, with an alkyl group (e.g., octyl, decyl, hexadecyl, 2-ethylhexyl), an alkoxy group (e.g., dodecyloxy, hexadecyloxy), a sulfido group (e.g., hexadecylsulfido), a substituted amino group (e.g., heptadecylamino), an octylcarbamoyl group, an octanoyl group and a decylsulfamoyl group. Also preferably, the group is substituted with two or more such substituents. Apart from the substituents mentioned above, the group may also be substituted with any of a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, and a sulfo group.

In formula (1), when R is a heterocyclic group, it is preferably a 5- to 7-membered heterocyclic group like D, more preferably a 5-or 6-membered heterocyclic group, most preferably a 6-membered heterocyclic group. Concrete examples of the skeleton are described in, for example, Iwanami Dictionary of Physicochemistry, Edition 3, Supplementary Edition, (published by Iwanami Shoten), Appendix Chap. 11, Nomenclature in Organic Chemistry, Table 4, Names of Principal Heterocyclic Monocyclic Compounds, p. 1606, and Table 5, Names of Principal Condensed Heterocyclic Compounds, p. 1607. Like the aryl group, the heterocyclic group may be substituted, and it is preferably substituted with a substituent that contains a linear or branched alkyl group having at least 8 carbon atoms. Also preferably, the heterocyclic group is substituted with two or more such substituents. Apart from the substituents mentioned above, the group may also be substituted with any of a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, and a sulfo group.

In formula (1), it is desirable that at least one of m groups of Rs contains an ester bond. m indicates an integer of from 2 to 11. When m is 2 or more, then two or more Xs and Rs may be the same or different. Preferably, m is 3 or more.

Of the compounds of formula (1), preferred are those of the following formula (3):

In formula (3), X¹, X² and X³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof.

When X¹, X² and X³ are single bonds, then the substituents may directly bond to the heterocyclic group via the nitrogen atom having a free atomic valence, like in piperidine, or even when the heterocyclic group does not have a free atomic valence, the substituents each may bond to the hetero atom to form onium salts such as oxonium salts, sulfonium salts or ammonium salts. When X¹, X² and X are not single bonds, they are any of a group NR¹ (where R¹ represents an alkyl group having from 1 to 30 carbon atoms, or a hydrogen atom), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof, for example, an oxycarbonyl group, an aminocarbonyl group, an ureylene group, an oxysulfonyl group or a sulfamoyl group. Preferred are a sulfur atom and a group NR¹. R¹ is preferably an alkyl group having at most 3 carbon atoms, or a hydrogen atom. More preferably, the group NR¹ is an imino group (—NH—).

In formula (3), R¹¹, R¹² and R¹³ each independently represent an alkyl group, analkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, and at least one of R¹¹, R¹² and R¹³ contains an ester bond.

When R¹¹, R¹² and/or R¹³ each are an alkyl group, it preferably has from 1 to 30 carbon atoms, more preferably from 2 to 30, even more preferably from 4 to 30, still more preferably from 6 to 30 carbon atoms. The alkyl group may be linear or branched. It may be substituted. Examples of the substituent include a halogen atom, an alkoxy group (e.g., methoxy, ethoxy, methoxyethoxy, phenoxy), a sulfido group (e.g., methylthio, ethylthio, propylthio), an alkylamino group (e.g., methylamino, propylamino), an acyl group (e.g., acetyl, propanoyl, octanoyl, benzoyl), an acyloxy group (e.g., acetoxy, pivaloyloxy, benzoyloxy), a hydroxyl group, a mercapto group, an amino group, a carboxyl group, a sulfo group, a carbamoyl group, a sulfamoyl group, and an ureido group.

When R¹¹, R¹² and/or R¹³ each are an alkenyl group or an alkynyl group, the number of carbon atoms constituting the group and the morphology of the group may be the same as those of the alkyl group, and the group may be substituted like the alkyl group.

When R¹¹, R¹² and/or R¹³ each are an aryl group, it includes a phenyl group, an indenyl group, an α-naphthyl group, a β-naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, and pyrenyl group. Preferred are a phenyl group and a naphthyl group. Preferably, the aryl group is substituted with a substituent that contains a linear or branched alkyl group having at least 8 carbon atoms, for example, with an alkyl group (e.g., octyl, decyl, hexadecyl, 2-ethylhexyl), an alkoxy group (e.g., dodecyloxy, hexadecyloxy, 2-hexyldecyloxy, hexyloxyethyleneoxyethyleneoxy), a sulfido group (e.g., hexadecylthio), a substituted amino group (e.g., heptadecylamino), an octylcarbamoyl group, an octanoyl group and a decylsulfamoyl group. More preferably, the group is substituted with two or more such substituents. Apart from the substituents mentioned above, the group may also be substituted with any of a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, and a sulfo group.

When R¹¹, R¹² and/or R¹³ each are a heterocyclic group, it is preferably a 5- to 7-membered heterocyclic group like D in formula (1), more preferably a 5- or 6-membered heterocyclic group, most preferably a 6-membered heterocyclic group. Concrete examples of the skeleton are described in, for example, Iwanami Dictionary of Physicochemistry, Edition 3, Supplementary Edition, (published by Iwanami Shoten), Appendix Chap. 11, Nomenclature in Organic Chemistry, Table 4, Names of Principal Heterocyclic Monocyclic Compounds, p. 1606, and Table 5, Names of Principal Condensed Heterocyclic Compounds, p. 1607. Like the aryl group, the heterocyclic group is preferably substituted with a substituent that contains a linear or branched alkyl group having at least 8 carbon atoms. Also preferably, the heterocyclic group is substituted with two or more such substituents. Apart from the substituents mentioned above, the group may also be substituted with any of a halogen atom, a hydroxyl group, a cyano group, a nitro group, a carboxyl group, and a sulfo group.

Of the compounds of formula (3), more preferred are those of the following formula (4):

In formula (4), X²¹, X²² and X²³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof.

When X²¹, X²² and X²³ are single bonds, then the substituents may directly bond to the heterocyclic group via the nitrogen atom having a free atomic valence, like in piperidine, or even when the heterocyclic group does not have a free atomic valence, the substituents each may bond to the hetero atom to form onium salts such as oxonium salts, sulfonium salts or ammonium salts. When X²¹, X²² and X²³ are not single bonds, they are any of a group NR¹ (where R¹ represents an alkyl group having from 1 to 30 carbon atoms, or a hydrogen atom), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof, for example, an oxycarbonyl group, an aminocarbonyl group, an ureylene group, an oxysulfonyl group or a sulfamoyl group. Preferred are a sulfur atom and a group NR¹. R¹ is preferably an alkyl group having at most 3 carbon atoms, or a hydrogen atom. More preferably, the group NR¹ is an imino group (—NH—).

R²¹, R²² and R²³ each independently represent a substituent, and at least one of R²¹, R²² and R²³ contains an ester bond. The substituents R²¹, R²² and R²³ preferably contain any of a halogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, acyano group, a hydroxyl group, a nitro group, a carboxyl group, an alkoxy group, an aryloxy group, a silyloxy group, a hetero-oxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group, an acylamino group, an aminocarbonylamino group, an alkoxyaminocarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkyl and arylsulfonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic-thio group, a sulfamoyl group, a sulfo group, an alkyl and arylsulfinyl group, an alkyl and arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, a carbamoyl group, an aryl and heterocyclic-azo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, and a silyl group. The substituents R²¹, R²² and R²³ may be substituted with at least one substituent selected from these groups. At least one of R²¹, R²² and R² contains an ester bond. In particular, at least one of R²¹, R²² and R²³ is preferably an alkoxy group substituted with a substituent that contains an ester bond-containing, linear or branched alkyl group. a21, a22 and a23 each independently indicate an integer of from 1 to 5. When a21, a22 and a23 each are 2 or more, then the substituents R²¹, R²² and R²³ may be at any position. The plural R²¹s, R²²s and R²³S may be the same or different.

The compound of formula (2) to be in the lubricant composition of the invention is described in detail.

In formula (2), R³¹ represents a linear or branched alkyl, alkenyl or alkynyl group, or a cycloalkyl group. Preferably, the group is substituted with a substituent that contains an alkyl chain having at least 4 carbon atoms in total, an alkyleneoxy chain (e.g., oligoalkyleneoxy chain), a polyfluoroalkyl chain having at least 2 carbon atoms in total, or an organic polysilyl chain. More preferably, it is substituted with an alkyleneoxy chain-containing substituent, for example, with an ethyleneoxy group-containing substituent. Above all, it is especially preferably an alkyl group substituted with an alkyleneoxy chain-containing substituent.

The organic polysilyl chain above is such that having a silicon-atom-containing group as a side chain of a long-chain substituent (e.g., poly(p-trimethylsilylstyrene) and poly(1-trimethylsilyl-1-propine)), or such that having silicon atoms in a main chain of a long-chain substituent, where the latter is more preferable. Preferable long-chain substituents having silicon atoms in the main chain are straight-chain, branched, cyclic or polycyclic long-chain substituents having a repetitive unit represented by the formula (s) below: —[Si(R^(s1))(R^(s2))—X]—  (s)

In formula (s), R^(s1) and R^(s2) each independently represent a substituent. R^(s1) and R^(s2) may be bonded together to form a cyclic structure. Examples of the substitutents include halogen atoms, alkyl groups (including cycloalkyl groups and bicycloalkyl groups), alkenyl groups (including cycloalkenyl groups and bicycloalkenyl groups), alkynyl groups, aryl groups, heterocyclic groups, cyano, hydroxyl, nitro, carboxyl, alkoxy groups, aryloxy groups, silyloxy groups, heterocyclic oxy groups, acyloxy groups, carbamoyloxy groups, alkoxycarbonyloxy groups, aryloxycarbonyloxy groups, amino groups (including anilino group), acylamino groups, aminocarbonylamino groups, alkoxycarbonylamino groups, aryloxycarbonylamino groups, sulfamoylamino groups, alkyl- and arylsulfonylamino groups, mercapto group, alkylthio groups, arylthio groups, heterocyclic thio groups, sulfamoyl group, sulfo group, alkyl- and arylsulfinyl groups, alkyl- and arylsulfonyl groups, acyl groups, aryloxycarbonyl groups, alkoxycarbonyl groups, carbamoyl group, aryl- and heterocyclic azo groups, imide groups, phosphino groups, phosphinyl groups, phosphinyloxy groups, phosphinylamino groups, and silyl groups. The substituents R.sup.11 to R.sup.13 also include above substituents further substituted with at least one of such substituents. Alkyl group is the most preferable substituent. X represents an atomic group which consists of at least one of an oxygen atom, a nitrogen atom, an alkylene group, a phenylene group, a silicon atom, a metal atom. X is preferably an oxygen atom or an atomic group composed of an oxygen atom and an alkylene group, and more preferably, an oxygen atom. The notation “p” is an integer of 1 to 200, and preferably 3 to 30. Examples of the organic polysilyl chain include polysiloxane, polysilazane, polysilmethylene, polysilphenylene, polysilane, and polymetallosiloxane.

Examples of the compounds of formula (3) are mentioned below as the typical examples of the compounds of formula (1). However, the invention should not be restricted at all by the following examples.

X¹ = X² = X³ R¹¹ = R¹² = R¹³ N-1 

—(CH₂)₁₀CO₂CH₃ N-2 

—(CH₂)₁₀CO₂C₈H₁₇ N-3 

—(CH₂)₁₀CO₂C₁₂H₂₅ N-4 

—(CH₂)₁₀CO₂CH₂CH₂C₈F₁₇ N-5 

N-6 

—(CH₂)₄CO₂—(CH₂CH₂O)₂C₆H₁₃ N-7 

—(CH₂)₇CO₂—(CH₂CH₂O)₂C₆H₁₃ N-8 

—(CH₂)₁₀CO₂—(CH₂CH₂O)₂C₆H₁₃ N-9 

—(CH₂)₁₀CO₂—(CH₂CH₂O)₃CH₃ N-10

—(CH₂)₁₀CO₂—(CH₂CH₂O)₄C₁₂H₂₅ N-11

N-12

N-13

N-14

N-15

N-16

N-17

N-18

N-19

N-20

N-21

N-22

N-23

N-24

N-25

N-26

N-27

N-28

N-29

N-30

X¹ = X² X³ R¹¹ = R¹² = R¹³ N-31

—S—

N-32

—S—

N-33

—S—

N-34

—S—

N-35

—S—

N-36

—S—

N-37

—S—

N-38

—S—

N-39

—S—

N-40

—S—

N-41

—S—

N-42

—S—

N-43

—S—

N-44

—S—

N-45

—S—

N-46

—S—

N-47

—S—

N-48

—S—

N-49

—S—

N-50

—S—

Typical examples of the compounds of formula (2) are mentioned below. However, the invention should not be restricted at all by the following examples. A-1  CH₃CH₂O—CH₂—COOH A-2  CH₃OCH₂CH₂O—CH₂—COOH A-3  CH₃OCH₂CH₂OCH₂CH₂O—CH₂—COOH A-4  C₄H₉OCH₃CH₂OCH₂CH₂O—CH₂—COOH A-5  C₆H₁₃OCH₃CH₂OCH₂CH₂O—CH₂—COOH A-6  C₁₂H₂₅OCH₃CH₂OCH₂CH₂O—CH₂—COOH A-7  CH₃OCH₂CH₂OCH₂CH₂OCH₂CH₂O—CH₂—COOH A-8  C₆H₁₃CH₂CH₂OCH₂CH₂OCH₂CH₂O—CH₂—COOH A-9  CH₃OCH₂CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₂O—CH₂—COOH A-10 C₁₂H₂₅OCH₂CH₂OCH₂CH₂OCH₂CH₂OCH₂CH₂OCH₂—COOH A-11

A-12

A-13

A-14

A-15

A-16

A-17

A-18

A-19

A-20

A-21

A-22

A-23

A-24

A-25

A-26 CHF₂CF₂CF₂—O—CH₂—COOH A-27

A-28

A-29

A-30

The blend ratio of the compound of formula (1) and the compound of formula (2) is preferably from 0.5 to 5, more preferably from 1 to 4, even more preferably from 2 to 4, in terms of the ratio by mol of the compound of formula (2) to the compound of formula (1) of being 1. Combining the compounds of formulae (1) and (2) improves the flowability of the resulting composition and improves the lubricity at low temperatures thereof. In addition, the lubricant composition may maintain a low friction factor within a broad temperature range covering from low temperatures and high temperatures. Further, the lubricant composition exhibits excellent low-friction lubrication potency under various lubrication conditions, for example, for liquid lubrication and boundary lubrication. When the amount of the compound of formula (2) is larger than that of the compound of formula (1), the adsorption of the lubricant composition onto friction faces is improved, and the viscosity thereof may be more effectively controlled, and, in addition, the temperature range within which the lubricant composition may keep a low friction factor may be broadened.

One preferred combination of the compound of formula (1) and the compound of formula (2) is, for example, a combination of a compound of formula (3) where X¹, X² and X³ are imino groups (—NH—) and a compound of formula (2) where R³¹ is an alkyleneoxy chain-containing substituent (e.g., alkyleneoxy chain-containing alkyl group). More preferably, a compound of formula (4) where X²¹, X²² and X²³ are imino groups (—NH—) is combined with a compound of formula (2) where R³¹ is an alkyleneoxy chain-containing substituent (e.g., alkyleneoxy chain-containing alkyl group).

The compounds to constitute the lubricant composition of the invention may serve as a base oil of lubricant compositions by themselves. If desired, they may be mixed with any other mineral oil or synthetic oil that is generally used as a base oil for lubricant compositions, therefore serving as the base oil of the lubricant composition of the invention. The mineral oil and the synthetic oil that may be combined with the compounds in the invention to form mixed base oil are not specifically defined, and may be any ones generally used as a base oil for lubricant. Any mineral oil, synthetic oil and their mixture may correspond to them. The mineral oil includes, for example, solvent-refined raffinate that is obtained through treatment of a lubricant material derived from normal-pressure or reduced-pressure distillation of a paraffin-base, intermediate-base or naphthene-base crude oil, with an aromatic extraction solvent such as phenol, furfural or N-methylpyrrolidone; a hydrogenated oil obtained by contacting a lubricant material with hydrogen under hydrogenation condition in the presence of a hydrogenation catalyst of cobalt, molybdenum or the like held on a silica-alumina carrier; a hydro-cracked oil obtained by contacting a lubricant material with with hydrogen under severe cracking condition in the presence of a hydro-cracking catalyst; an isomerized oil obtained by contacting wax with hydrogen under isomerization condition in the presence of an isomerization catalyst; and lubricant fractions obtained through combination of such a solvent-refining step, a hydrogenation step, a hydro-cracking step and an isomerization step. In particular, mineral oils having a high viscosity index that are obtained in the hydro-cracking process or the isomerization process are preferred for use in the invention. These production processes may have any ordinary dewaxing, hydrogenation-finishing and clay treatment in any desired manner. Examples of the mineral oil are light-neutral oil, middle-neutral oil, heavy-neutral oil and bright stock. These may be mixed in any desired manner so that the resulting mixture could satisfy the desired requirements, and the mixture may serve as a base oil. The synthetic oil includes, for example, poly-α-olefin, α-olefin oligomer, polybutene, alkylbenzene, polyol-ester, dibasic acid ester, polyoxyalkylene glycol, polyoxyalkylene glycol ether, and silicone oil. One or more of these base oils may be used either singly or as combined. If desired, mineral oil and synthetic oil may be combined for use herein. These ordinary base oils that may be used for the mixed base oil in the lubricant composition of the invention generally have a kinematic viscosity of from 2 to 20 mm²/sec at 100° C., preferably from 3 to 15 mm²/sec. A mixed base oil having an optimum kinematic viscosity is selected for the lubricant composition of the invention so that it may satisfy the lubrication conditions for the mechanical friction slide members to which the lubricant composition of the invention is to be applied.

Regarding the blend ratio with the ordinary base oil in the lubricant composition of the invention, in general, the proportion of the former ester structure-having compound is from 0.1 to 20% by weight and that of the latter ordinary base oil, or that is, mineral oil and/or synthetic oil is from 80 to 99.9% by weight, relative to the overall amount of the base oil. Preferably, the proportion of the lubricant composition of the invention is from 0.1 to 10% by weight, most preferably from 0.1 to 5% by weight. However, since the lubricant composition of the invention may serve, by itself, as a base oil of lubricant compositions, and its single use is often more effective, providing a low friction factor in a broad temperature range even under severe lubrication conditions and additionally exhibiting a better effect for abrasion resistance.

For ensuring its practicability to various applications, the lubricant composition of the invention may contain, if desired, various additives that are generally used in lubricant such as bearing oil, gear oil, power transmission oil or the like, for example, wearing inhibitor, extreme-pressure agent, antioxidant, viscosity index improver, detergent dispersant, metal inactivator, corrosion inhibitor, rust inhibitor, defoaming agent and the like not detracting from the object of the invention.

The lubricant composition of the invention is characterized in that it provides a low friction factor even under severe lubrication conditions, and has good abrasion resistance and good extreme-pressure resistance. The lubricant composition of the invention may be prepared by mixing a compound of formula (1), preferably a compound having a structure of formula (3), more preferably formula (4), and a compound of formula (2), followed by optimizing the resulting mixture to be a liquid even at −40° C., and this may be usable even at low temperatures and its practicability is therefore broadened.

As having the good characteristics as above, the lubricant composition of the invention may be used in any severe lubrication conditions. For example, even in severe lubrication conditions under which conventional lubricants such as lube oil or grease may cause lubrication failure, the lubricant composition of the invention still exhibits good abrasion resistance and has a low friction factor without causing seizure, and therefore it is an energy-saving good lubricant favorable to bearings and gears that are driven under severe lubrication conditions. Moreover, since the lubricant composition of the invention does not cause seizure even under severe lubrication conditions, it contributes to improving the reliability of slide devices and to down-sizing slide devices.

The characteristics of the invention are described more concretely with reference to the following Examples and Comparative Examples. The material, its amount and its blend ratio, and the treatment and the treatment order in the following Examples may be suitably changed and modified not overstepping the scope and the sprit of the invention. Accordingly, the scope of the invention should not be limitatively interpreted from the Examples shown hereinunder.

EXAMPLES

Lubricant compositions (Examples 1 to 6) shown in the following Table 1 were prepared, in which N-8, N-14, N-28 and A-3 were used as the compounds of formulae (1) and (2), and the lubricant base oil as in the Tables. Comparative lubricant compositions (Comparative Examples 1 to 6) were prepared as in the following Table 2, in which lubricant base oil alone was used, or N-28 and a comparative compound M-2 mentioned below were used. Comparative Compound (M-2):

Thus prepared, these compositions were tested according to the friction test mentioned below, and the friction factor was measured in every case. In the test, the friction factor was measured by the use of an abrasive friction tester (SRV abrasive friction tester).

[Test Condition]

-   The test is a cylinder-on-plate test. -   Test piece (friction piece): SUJ-2 -   Plate: φ24×6.9 mm -   Cylinder: φ11×15 mm -   Temperature: 80° C. -   Load: 400 N -   Amplitude: 1.5 mm -   Frequency: 50 Hz -   Time: 5 minutes after the start of the test

The result of Examples 1 to 6 is given in Table 1; and the result of Comparative Examples 1 to 6 is in Table 2. TABLE 1 Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 Compounds of N-8/ N-8/ N-14/ N-14/ N-28/ N-28/ the invention A-3 A-3 A-3 A-3 A-3 A-3 mol ratio 1/1 1/3 1/1 1/3 1/1 1/3 (mol/mol) wt. % 100 100 100 100 100 100 Lubricant base oil wt. % pentaerythritol — — — — — — ester*1 alkylbenzene*2 — — — — — — naphthene-base — — — — — — mineral oil paraffin-base — — — — — — mineral oil SRV abrasive 0.040 0.037 0.025 0.020 0.024 0.019 friction test, @400 N, 80° C. friction factor *1: pentaerythritol hexanoate *2: alkylbenzene with C10 alkyl group

TABLE 2 Com- Com- Com- Com- Com- Com- parative parative parative parative parative parative Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 Compounds of N-28/ N-28/ the invention M-2 M-2 mol ratio 1/1 1/3 (mol/mol) wt. % 100 100 Lubricant base oil wt, % pentaerythritol 100 — — — — — ester*1 alkylbenzene*2 — 100 — — — — naphthene-base — — 100 — — — mineral oil paraffin-base — — — 100 — — mineral oil SRV abrasive 0.210 0.230 0.250 0.230 0.060 0.055 friction test, @400 N, 80° C. friction factor *1: pentaerythritol hexanoate *2: alkylbenzene with C10 alkyl group

From the data of Examples and Comparative Examples in these Table 1 and Table 2, it is understood that, when the complex formed of the combination of the invention is used as a lubricant, then the resulting lubricant composition exhibits much better abrasion resistance.

The present disclosure relates to the subject matter contained in Japanese Patent Application No. 354773/2003 filed on Oct. 15, 2003, which is expressly incorporated herein by reference in its entirety.

The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The description was selected to best explain the principles of the invention and their practical application to enable others skilled in the art to best utilize the invention in various embodiments and various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention not be limited by the specification, but be defined claims set forth below. 

1. A lubricant composition containing a compound of the following formula (1) and a compound of the following formula (2):

wherein D represents a cyclic group capable of bonding to m groups of side branches; X independently represents a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R independently represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group; m indicates an integer of from 2 to 11,

wherein R³¹ represents an alkyl group, analkenyl group, an alkynyl group, or a cycloalkyl group.
 2. The lubricant composition of claim 1, wherein D in formula (1) is a 5- to 7-membered heterocyclic group.
 3. The lubricant composition of claim 1, wherein at least one of m groups of Rs in formula (1) contains an ester bond.
 4. The lubricant composition of claim 1, wherein the compound of formula (1) is represented by the following formula (3):

wherein X¹, X² and X³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R¹, R¹² and R¹³ each independently represent an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group, and at least one of R¹¹, R¹² and R¹³ contains an ester bond.
 5. The lubricant composition of claim 4, wherein X¹, X² and X³ in formula (3) are a sulfur atom or a group NR¹.
 6. The lubricant composition of claim 5, wherein R¹ is an alkyl having 3 or less carbon atoms or a hydrogen atom.
 7. The lubricant composition of claim 4, wherein X¹, X² and X³ in formula (3) are —NH—.
 8. The lubricant composition of claim 1, wherein the compound of formula (1) is represented by the following formula (4):

wherein X²¹, X²² and X²³ each independently represent a single bond, a group NR¹ (where R¹ represents a hydrogen atom, or an alkyl group having from 1 to 30 carbon atoms), an oxygen atom, a sulfur atom, a carbonyl group, a sulfonyl group, or a divalent linking group of a combination thereof; R²¹, R²² and R²³ each independently represent a substituent, and at least one of R²¹, R²² and R²³ contains an ester bond; a21, a22 and a23 each independently indicate an integer of from 1 to
 5. 9. The lubricant composition of claim 8, wherein X²¹, X²² and X²³ in formula (4) are a sulfur atom or a group NR¹.
 10. The lubricant composition of claim 8, wherein R¹ is an alkyl having 3 or less carbon atoms or a hydrogen atom.
 11. The lubricant composition of claim 8, wherein X²¹, X²² and X²³ in formula (4) are —NH—.
 12. The lubricant composition of claim 8, wherein at least one of R²¹, R²² and R²³ in formula (4) is an alkoxy group substituted with a substituent having an ester bond-containing, linear or branched alkyl group.
 13. The lubricant composition of claim 1, wherein R³¹ in formula (2) is an alkyl, alkenyl, alkynyl or cycloalkyl group substituted with a substituent that contains an alkyl chain having at least 4 carbon atoms in total, an alkyleneoxy chain, a polyfluoroalkyl chain having at least 2 carbon atoms in total, or an organic polysilyl chain.
 14. The lubricant composition of claim 1, wherein R³¹ in formula (2) is an alkyl group substituted with an alkyleneoxy chain-containing substituent.
 15. The lubricant composition of claim 1, wherein the compound of formula (1) and the compound of formula (2) form complexes.
 16. The lubricant composition of claim 1, which contains from 0.5 to 5 mols of the compound of formula (2) relative to one mol of the compound of formula (1).
 17. The lubricant composition of claim 1, which contains from 1 to 4 mols of the compound of formula (2) relative to one mol of the compound of formula (1).
 18. The lubricant composition of claim 1, which contains from 2 to 4 mols of the compound of formula (2) relative to one mol of the compound of formula (1).
 19. The lubricant composition of claim 1, which contains the compound of formula (2) more than the compound of formula (1).
 20. The lubricant composition of claim 1, which consists of the compound of formula (1) and the compound of formula (2). 